<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>隐藏属性</title>

    <style>
        .a {
            display: none;
            width: 100px;
            height: 100px;
            background-color: black;
        }
        
        .b {
            width: 100px;
            height: 100px;
            background-color: bisque;
        }
        
        .c {
            float: right;
            background-color: aqua;
        }
        
        .c:hover .a {
            display: block;
        }
    </style>


</head>

<body>




    <div class="b">

    </div>

    <div class="c">
        出现了
        <div class="a">

        </div>

    </div>


</body>

</html>